The present invention relates to a method of artificially forming patina on copper products, and more particularly to a method of artificially and rapidly forming uniform patina on copper product surfaces without causing environmental problems.
Patina formed on the surfaces of copper products advantageously prevents oxidization and corrosion of copper products and inhibits mold from growing on their surfaces. Another advantage of patina formed on the surfaces of copper products is decorative coloring, improving the appearance of copper products. Such advantages are appreciated in various copper works in fine arts, industrial arts, sculptures, monuments, architectures (particularly roofs and decorations) and the like having patina uniformly formed on their surfaces. Patina has also lately been used for various researches such as the creation of aseptic conditions by patina, medical applications of patina, hygienic applications of patina such as utilization of antibacterial effects, the influence of patina on plants and animals, etc.
Conventionally known as the artificial formation of patina on copper surfaces are electrolytic methods and acid application methods. In the electrolytic methods as exemplified in Japanese Patent Laid-Open No. 64-4493, a copper anode is eroded in an electrolytic solution, an electrolytic reaction causing patination on the surface of the copper anode. The electrolytic methods are, however, encountered with such problems that they are not suitable for or cannot be applied to large-scale copper products, particularly outdoor constructions such as monuments and architectures because it is difficult to process such copper products in an electrolytic solution.
In the acid application methods as exemplified in Japanese Patent Laid-Open No. 62-99547, an artificial patination solution composed mainly of hydrochloric acid and acetic acid is applied to copper products to cause patination. In these methods, however, the operations tend to be dangerous for workers, involving risks of generating acid gases detrimental to the environment. Furthermore, for processing copper products such as bronze statutes and architectures of temples and shrines often designated as cultural assets, the acid application methods cannot be used because acids may damage copper products.
For the above-mentioned reasons, neither the electrolytic methods nor the acid application methods can be used in processing outdoor constructions and large-scale copper products.
It is, thus, an object of the present invention to provide a method of artificially and rapid forming uniform patina on surfaces of copper products such as outdoor constructions and large-scale copper products without causing environmental problems.